W3C home > Mailing lists > Public > www-rdf-interest@w3.org > November 2000

Re: Statements/Reified statements

From: Sergey Melnik <melnik@db.stanford.edu>
Date: Wed, 22 Nov 2000 15:21:17 -0800
Message-ID: <3A1C54ED.B240C986@db.stanford.edu>
To: Jonas Liljegren <jonas@rit.se>
CC: RDF Interest Group <www-rdf-interest@w3.org>
Jonas Liljegren wrote:
> 
> Sergey Melnik <melnik@db.stanford.edu> writes:
>
> > Pierre-Antoine CHAMPIN wrote:
> > > ...
> > > First, Statements and Reified statements are not the same thing.
> >
> > Although this is consistent with the spec, I believe there are
> > significant advantages both for understanding and manipulating
> > reified statements if these two notions are merged into one.
> >
> > Can you (or anyone) list some use cases where it is beneficial to
> > make this distinction?
> 
>  1. It let us the reified statement as a stating
> 
>  2. It saves us the trouble of joining reified statements with given
>     URIs from diffrent models.

The above examples can be perfectly dealt with when a statement is a
resource.

> > I can think of several cases, in which distinguishing statements
> > vs. reified statements makes things a lot more complicated.  Just
> > consider a database query that retrieves all assertions made about a
> > statement (by anyone).
> 
> Could it be something like this?
> 
> select * from arc where subj in ( select id from arc where pred=? and
> subj=? and obj=?)

Well, Jonas, this approach is practically equivalent with the one that I
have in mind (except that statement IDs are not unique).

Notice that now you have another trouble: you have to rematerialize the
quad statements if you want to be spec compliant. What about a query
like

	select * from arc where pred = rdf:predicate
or
	select * from arc where pred = rdf:type and obj = rdf:Statement

?
Received on Wednesday, 22 November 2000 18:03:23 GMT

This archive was generated by hypermail 2.2.0+W3C-0.50 : Monday, 7 December 2009 10:51:46 GMT